


The Shadows that Define our Every Sunny Day

by BronzedViolets



Category: Sherlock (TV)
Genre: All The Tropes, Alternate Universe, Anal Fingering, Anal Sex, Bloodplay, Blow Jobs, Bottom Sherlock Holmes, Bottom!Lock, Celtic Mythology & Folklore, Come as Lube, Cutting, First Kiss, First Time, Halloween, I'm not even ashamed any more, Knotting, M/M, Minor Character Death, Non-Human John, Possessive John, Resolved Sexual Tension, Samhain, Soul Bond, Top John, Transformation, Unresolved Sexual Tension, Virgin Sherlock, all hallows eve, promises promises, top!John, twitching cocks
Language: English
Status: Completed
Published: 2016-11-15
Updated: 2016-11-15
Packaged: 2018-08-30 22:10:35
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 8,875
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/8551087
Author URL: https://archiveofourown.org/users/BronzedViolets/pseuds/BronzedViolets
Summary: “They were living together only a few weeks before Sherlock noticed it. Everything about John screamed practical and straightforward except for this. If the detective hadn't known better he would have said John was superstitious. It was little things at first, like nodding at magpies whenever he saw them or only chatting up women on Tuesdays. But that wasn't quite right. If these peculiarities were superstitions, they were ones he had never come across before. Finally, Sherlock chalked it up to an atypical symptom of his flatmate’s PTSD and left it at that. He would have never thought of it again until Autumn stole across the city and John started acting, well… stranger.”





	

**Author's Note:**

> Written on commission for a lovely friend.
> 
> Also I am finally putting my Uni class in Celtic literature to work! Can't say my professor would be proud. Or would he….
> 
> Translation of the Gaelic phrases are available in the end notes.
> 
> As always, a million thanks to my amazing beta SuperBlue! 
> 
> If you are interested in commissioning a fic or some mediocre art or just want to chat with me, you can find me on Tumblr @ http://bronzedviolets.tumblr.com/
> 
> P.s Comments are always welcome ( :
> 
> Happy Halloween!

**Halloween Night**

By the dying light of the fire, Sherlock takes John into him for the first time.

It is too much and too rough but it's still not quite enough. John pounds him harder, until the firm knot at the base of his cock is so big he can barely move, their frantic coupling reduced to a stuttering grind. When Sherlock can’t bear it any more, when he feels he will die or go mad with wanting, finally, _finally_ , sharp teeth sink into the meat of his shoulder. He shatters, a wordless scream caught in his throat, semen pumping out onto the rug beneath him. Then darkness….

**10 months earlier**

They were living together only a few weeks before Sherlock noticed. Everything about John screamed practical and straightforward, except for this. If the detective hadn't known better he would have said John was superstitious.

It was little things at first, like nodding at magpies whenever he saw them or only chatting up women on Tuesdays. But that wasn't quite right. If these peculiarities were superstitions, they were ones he had never come across before. Finally, Sherlock chalked it up to atypical symptoms of his flatmate’s PTSD and left it at that. He would have never thought of it again until Autumn stole across the city and John started acting, well… stranger.

** One week before Halloween **

As the leaves turned from green to gold, John’s weekly dates dwindled to zero and his masturbatory frequency increased by a whopping factor of seven. Not that he was keeping track (much) but Sherlock couldn’t help but take notice when John’s thrice weekly ritual of self-pleasure was replaced with a daily morning wank in the shower followed by another session or two at night after he retired to his room.

Under normal circumstances, Sherlock would have been delighted. When John forwent the carnal pleasures of women chatted up in bars, it gave him additional opportunities to clandestinely catalogue (for purely scientific reasons of course) the fascinating range of sounds and sighs John made when approaching climax.

Unfortunately, during the same period of time, when they weren’t on a case, John had spent progressively less time in the common areas of the flat, and more and more time sequestered in the privacy of his room.

Sherlock was quickly running out of patience, as well as lube. He’d been wanking himself half raw every night to the chorus of moans and grunts drifting down from upstairs and the worst part was he couldn't enjoy it properly. Somehow, between the chases and the murders, Sherlock had grown to care for the domesticity of tea in the kitchen and long nights of crap telly on the sofa. Even though John was right upstairs (albeit making delicious sounds) Sherlock missed him. It was intolerable.

Something had to be done.

If it had just been sex, Sherlock was sure he could have muddled through despite his relative inexperience. He knew he was attracted to John, his rugged good looks and his quiet competence never failed to spark something deep in his groin. When John passed by him on the stairs and Sherlock caught a trace of his scent, the musk of male overlaid with tea and antiseptic from the surgery never failed to spark a Pavlovian erection.

With all the smouldering looks between them, it should’ve been simple to bridge the gap between that and sex; John needed sexual stimulation, he could give John sex and they would both be happy. QED.

There was just one small ( _large_ ) problem.

Sherlock had always scorned self-deception and he refused to fall prey to it himself. He was completely, honestly, _irrefutably_ in love with Dr John Watson. It gave him a crawling sick feeling to think that he could ruin things if he made a move and John rebuffed him.

Heartsick and unsatisfied, he fell into a fitful sleep at last.

**The day before Halloween**

John was just sitting down to a cup of tea after a long shift, when Sherlock came pounding up the stairs like an over-enthusiastic child. With a manic glint in his eyes, he announced it was _imperative_ that they recover a portable printing press from an archaeologist's house in Essex.

John happily dumped his tea down the sink before heading upstairs to grab his gun.

Despite the long day at the clinic, he was glad to have a case on. _Samhain_ was less than six hours away, and he was feeling restive. This time of year always made the fire in his blood run a little closer to the surface.

When he made his way down to the sitting room a few minutes later, Sherlock shoved his coat into his hand and pelted out of the room and down to the street to hail a taxi.

John followed at a more sedate pace, but he couldn’t help but grin. He hadn’t seen Sherlock this excited since Amy Georgia-Rae Ashton, Moriarty’s _very_ pregnant ex-lover, had gunned the criminal mastermind down mid-trial.

Once the two men were ensconced in a cab, Sherlock launched into a breathless story involving a fake inheritance, a murderer named Winter, Americans, and people with the surname Garrideb. By the time Sherlock had got to the second Garrideb, John still didn’t understand how any of that related to either archeology or printing. The rest of the ride was spent nodding and making appropriate noises of assent while Sherlock scrolled through his phone to show him pictures of their suspect.

From the grainy snaps, James Winter appeared to be a stocky man in his mid-forties with the smashed in nose and cauliflower ears of a habitual brawler. In all of the photos he had a wide smile that never quite reached his eyes. John was suddenly glad for the solid weight of the Sig at his back.

***

The taxi dropped them off on a shady laneway. Their destination was a large regency-era home, set well back from the street. John was no expert but he figured it was worth at least £800,000.

“Whose house is this anyway?”

“Nathan Garrideb.”  
  
“A third Garrideb then? Is he expecting us?” queried John with a grimace, already suspecting what the answer would be.  
  
“I shouldn’t think so. I have it on good authority that he’s been called away on business to Birmingham.”  
  
“So we’re breaking in aren’t we?”  
  
“Yup,” Sherlock replied with a wry grin. “Problem?”  
  
John sighed in mock resignation and shook his head.

When the taxi rounded the corner out of sight, they made their way through a privet hedge and around to the back of the house.

The back door was hanging open like a gaping mouth. Sherlock gave John a grim look before extracting his mobile from his pocket and firing off a text to Lestrade.

“Do you think we have company?” John asked, pitching his voice low so that it wouldn’t carry.

By the dim light of the street lamp, Sherlock closely examined the loose gravel of the garden.

“No, if you look carefully, you can see a set of footprints heading towards the house, and a second set, slightly deeper, as though he was carrying a heavy burden heading back out. It looks like our man found what he was looking for.”

“So what are we still doing here?”

“Looking for proof, if we’re lucky we’ll find it before the Yard arrives and mucks everything up.” Sherlock handed John one of the small torches he always had secreted in his Belstaff and together they padded through the door and into a deserted parlour.

John's first impression was of a conspicuous lack of paintings and objets-d’art he had come to expect in this sort of home. Instead, the owner’s tastes seemed to run to bric-à-brac and curios. A half dozen hat stands were lined up in military ranks on one side of the parlour, and framing the fireplace were a flock of butterflies each lovingly preserved in its own shadowbox.

Past the slightly macabre display, a set of switchback servant’s stairs lead to the second floor, while on the other side, over-large French doors led to the rest of the house.

“You take the upstairs, I'll take the downstairs,” Sherlock whispered before heading off into the gloom.

John let out a genuine sigh this time. He had no idea what sort of proof he was looking for, and Sherlock didn't seem inclined to enlighten him. Nonetheless, he flicked on his torch and cautiously made his way up the steps until the narrow stairs opened onto a dimly lit landing. Ahead of him, the main stairs stretched back down to what he assumed would be the front entranceway. To his right, the stairway continued up another half-flight before opening onto the top floor. At the end of the hall, a large stained glass window with a rose motif stained the floor with blood-coloured light. John ascended further, his shadow following playfully behind him in the flickering beam of the torch. Off the hallway were four open doors, each made of a wood stained so dark that they gave the illusion the crystal doorknobs were floating. John slipped through the first door into a spacious bathroom. A cream-coloured clawfoot tub occupied one side, with a commode, a bidet, and an ornate pedestal sink taking up the rest of the floor space. It would have been quite a lovely room save for the walls. From floor to ceiling they were covered with vintage tin signs. Fry’s Cocoa cried for attention next to Walnut Plug Tobacco, Coleman’s Starch, and Edinburgh Rope Company. John supposed one or two would have made the room seem homey but with dozens on display, he had the disconcerting impression that a catalogue had exploded. He eased the door of the large medicine cabinet open, but when he found nothing more interesting than paracetamol and plasters he closed it again.

Padding into the hall, he tried the second room. It was a large bedroom that was as unusual as the rest of the house. If you didn’t look up, the room seemed almost austere. There was a large wardrobe, a neatly made queen-sized bed, and a solitary bedside table with an understated Tiffany lamp. What set the room apart was the ceiling. Hundreds of hand blown glass spheres were strung from an exposed overhead beam.  Sherlock would probably be able to identify the makers, but John’s only impression was that each piece was simple but relatively well-made.  When he had assured himself he wasn’t about to be showered with broken glass if a draught disturbed the air, he made his way over to the wardrobe, half expecting it to be filled with pickled frogs. He was relieved to see nothing out of the ordinary. One side was taken up by a shelf of neatly folded socks, vests, and pants. The other side contained a rack of slacks, dress shirts and jumpers, and two suits; one grey, one black. A quick look at the labels revealed them to be off the rack.  
  
The third room was more interesting. John got the impression that this was where the occupant actually lived. As opposed to being limited to one passion, collections had been allowed to run riot. The overall impression was of a workshop crossed with a library. Bulging bookshelves circled the room, looming over visitors. The titles ranged from university tomes on archeology, to numismatics, and mechanical engineering. Bits and bobs of machinery took up most of the three small work benches. In the corner crouched a machine that looked like a gramophone crossed with a meat-grinder.  
  
At the far end of the room, flush underneath a gabled window, sat a solid oak desk with spindly chair tucked unobtrusively into the knee well. It was the only relatively clear spot in the whole room. By day the occupant would have a stunning view across the back garden, but the placement gave John a prickle of unease across his shoulder blades. At first he chalked the unsettled feeling down to the thought of someone sitting with their back to the door for any length of time, but he hadn’t lived this long by ignoring his gut instincts. He crept forward to take a closer look at the desk. There was a large patch free of dust where a bulky object had been recently removed. Probably the portable printing press Sherlock had been talking about. Next to the void was a stack of rectangular metal plates. He picked the top one up and flipped it over. For an instant it looked like gibberish before he realized that the printing was reversed. Squinting his eyes in the low light of his torch he deciphered the tiny print.

BANK OF ENGLAND

I PROMISE TO PAY THE BEARER ON DEMAND

THE SUM OF FIVE HUNDRED POUNDS.

John’s heart jumped in his chest like a live wire. What had started as a lighthearted housebreaking had become something else entirely. Winter hadn’t been looking for a run of the mill printing press. He was planning on counterfeiting bank notes. Worse, he had the press but not the plates… _Bugger_.

Without a second thought, John raced back towards the stairs, his shadow flickering ominously. He had to warn Sherlock that Winter was liable to be back any minute. He was only at the landing when a muffled grunt and a thud drifted up from the lower floor.

John crept down the rest of the stairs and right into the scene from a nightmare. Silhouetted by moonlight streaming through the windowpanes, were Sherlock and Winter. The thickset man had a gun pressed up against Sherlock’s temple with brutal force, finger resting on the trigger.  A quick glance identified it as a Glock 9mm, 17 shot magazine, with a trigger pull of only 5 lbs.  John’s blood turned to ice. There had obviously been a struggle as both were breathing heavily and Sherlock’s nose was sluggishly trickling blood. With a trigger pull weight that light, it would be sickeningly easy to fire the gun by accident, obliterating everything of value in John’s life in one fell swoop.  If it had happened on any other night he would have been able to stay in control.  Maybe he would have pulled his own gun and put a bullet neatly through the man’s head and no one would’ve been the wiser. Not on this night though, not so close to _Samhain,_ with the weight of the otherworld pressing down upon him. As it was, the look in Sherlock’s eyes did him in. Maybe it was something the detective had deduced about his captor, but they were the eyes of someone who knew he wasn’t walking away from this. For the first time in over a thousand years, John’s control... _snapped_.

***

Afterward, when Sherlock tried to replay the scene in his mind’s eye, he had trouble sorting out the order events had unfolded. One minute he had a gun to his head, wordlessly saying his goodbyes to John, and the next minute windows were exploding in a shower of glass, the pistol skittering across the floor, glowing like it had been heated in a forge. John was standing there in front of him like an avenging angel with a look in his eyes that made the hair on Sherlock’s arms stand on end. The atmosphere in the room was the electric blue silence right before a lightning strike. John’s eyes, normally a staid navy blue, were the burning gold of a sodium oxalate flame. Behind him, his shadow seemed to writhe and swell before stilling once more. To Sherlock’s right, Winter stumbled back, eyes stuttering between the blackened burn on his palm and the man before him.

John took a menacing step forward, the shadow at his feet pulsing and twisting in excitement. His voice was a growl.

“If Sherlock is hurt, I swear on my father’s grave that you will live an exceedingly long life and every minute of it will be filled with suffering.”

Winter made a low gasping noise in his throat, but speech appeared to be beyond him.

“I’m fine John,” Sherlock finally choked out, breaking the tense silence.

John turned to look at him, and the unfiltered love and protective rage in his eyes was so profound that it was Sherlock’s turn to stumble.

It seemed like their eyes were locked for an eternity when the the distant sounds of Lestrade’s team arriving shattered the fragile moment. John gave a sharp nod and, in a flash of movement, backhanded Winter with a bone-rattling thunk.

While the murderer crumpled like a pile of rags, a million thoughts crashed through Sherlock’s head at once.

John, glorious John, was so much _more_ than he seemed.

John who never touched an iron railing with his bare hands; John, who flirted only on Tuesday's and left sprigs of white heather on all of the window sills. There was so much data to explore, but it all paled in comparison to the burning certainty that John _loved_ him. That was the most staggering revelation of all.

The next 45 minutes were amongst the most painful of Sherlock’s life. By tacit agreement, they hadn’t spoken of what John had done, and by the time a baffled Lestrade took their statements, Sherlock was fairly vibrating out of his skin. John, on the other hand, looked ashen, and kept glancing at Sherlock out of the corner of his eye like he couldn’t quite figure out what he was still doing there.

The taxi ride home was even worse. With the shock of everything starting to fade, John was shaking with repressed emotion. Although Sherlock prided himself in reading his flatmate’s moods, from the minutiae of a turned down cuff or a certain set to his jaw, he was forced to acknowledge he was out of his depth. Unlike the raw love he had seen burning in John’s eyes at the house, something darker was now at play. Behind the composed mask, Sherlock glimpsed a potent maelstrom of emotion roiling under his skin. He couldn’t tell if what was flickering in his friend’s eyes was fear or rage, hunger or loss. The only thing he knew for certain, was that John was barely holding it in check.

When the taxi finally pulled up in front of 221 B, John climbed out like an automaton and marched woodenly up to the door, leaving Sherlock to pay the driver. This more than anything else shook Sherlock. _He_ was the one who swanned off leaving John to fumble in his pockets for cab fare. The sudden reversal in roles made him feel wrong-footed. Sherlock shook his head in disgust and tossed a few folded notes at the driver before following John up the stairs.

***

Sherlock carefully clicked the door to the flat behind him before turning to face the man who saved his life.

John stood in the middle of the room, eyes seemingly focused on the cold grate. When he heard the snick of the door closing he turned slowly towards Sherlock with the air of a man condemned.

Sherlock opened his mouth, not even sure what he was about to say, but before he could speak John cut him off with a sharp nod of his head.

“Wait. You have questions and I promise, before I go I will answer them.” With his fists clenched and his head bowed he was the perfect picture of despair.

All Sherlock could do was gape stupidly at him. When John just stared back, looking increasingly alarmed at his speechless friend, Sherlock managed to shake himself out of his stupor.

“Where are you going? You can’t go, you love me.” As soon as the words left his mouth he cringed.

It was like a bomb had been detonated in the room.

John took a shocked step back, incandescent with rage and near tears. “How dare you use that against me? Now of all times? You utter _bastard_.”

John had always taken up more space in a room than seemed possible for such a small man, but now even at 5’6” he was positively towering over Sherlock. With an uncharacteristic timidness, Sherlock looked away. It took him a moment to realise that what he was feeling coiling cold in his gut was  _fear._ He’d never stopped to think that John might leave him.

“Look at me Sherlock.” John’s voice was a commanding growl.

With his breath caught like a trembling bird in his throat, Sherlock forced himself to meet his flatmate’s eyes.

“We both know I am arse over tea kettle for you...and it is killing me but you made it clear you were married to your work and I would NEVER do something that made you uncomfortable . The things I have done for you- I ...But this is too much. Even from you…”

_Oh_... With blinding clarity everything crashed into place. John didn't know Sherlock loved him back. Sherlock couldn’t help himself, and a delighted laugh bubbled up out of his mouth.

The resultant look on John’s face was somewhere between murderous and baffled.

Sherlock stepped forward and when he spoke it was with a tenderness he'd almost forgotten he was capable of. “You really don't know, do you John?”

“I - I don’t understand.” The weight of hope unspoken hung heavily between them.

Sherlock took another step forward and raised a large hand to gently touch the weathered cheek of his best friend in the world. “John, you are everything to me. I mean… I can’t even begin to hypothesize _what_ you are… but I… I would be everything to you if you would have me.”

John let out a strangled sob of relief, blinking unshed tears from his eyes.

“Oh God Sherlock, you have no idea how much I want this. But fuck, if it had been any other night… It's bloody _Samhain_ in less than an hour and the veils are thinning, _I can feel it_. I know I wouldn’t be able to control myself.“

“Then don’t,” he replied, as though it was the simplest thing in the world.

“Fuck. You don’t understand.” John paced back and forth in the grip of inner turmoil.

“Then explain. Are you a demon?”

John gave a resigned sigh. Sherlock pushing where any sane person would have backed off was definitely familiar territory between them. “Not quite.” With a gesture of his blunt fingers towards the hearth, the logs began to smoulder and then burst into flames.

Sherlock gaped in wonder and fear as the flames danced, gold and silver and scarlet.

“What _are_ you?” he breathed.

John sighed and scrubbed his fingers through his short hair, a surprisingly human gesture despite the circumstances.

“ _Cù-Sìth_ , it's a Scots Gaelic word for-”

“Fairy dog, I know how to speak Gaelic John,” Sherlock admonished, his face scrunching up into his habitual expression when faced with mediocrity.

“Of course you do you prat.” John chuckled fondly. Trust Sherlock to still be Sherlock even in the face of a reality shattering revelation.

“How old _are_ you?”

“To be honest, I'm not sure. I was still young when the Romans laid the first stones of Hadrian’s wall. So around 2,000 give or take a few hundred years?”

“Are there more of you?”

“Of the _Cù-Sìth_? As far as I know Harry and I are the only ones left…”

“Left?” Sherlock parroted, before wincing at the banality of his question.

John continued speaking as though he hadn’t been interrupted, a grey melancholy shining in his eyes.

“There were twelve of us, born at the foot of the _Sgùrr a' Ghreadaidh_ mountains. We were raised to guard the battlefields of the fae and escort the fallen warriors to the gates of _Tir na Marbh_ when they passed. Their armies have been ashes for a millennia and a half now, the survivors scattered across the globe. There are so few of us left I rarely have to do my duty.”

“And your siblings, err... died?” Sherlock felt his lips twitch down in sympathy. For all Mycroft thrived on being an arse, the twat _was_ family and he knew his brother’s death would leave a wound that time wouldn’t heal. He couldn’t imagine bearing witness to the death of ten siblings. There was something so... _ordinary_ about it that …

“Why are you surprised?” John chided, correctly reading his expression. “You have seen me eat and sleep. We are flesh and blood like any other living thing. We are born, we live and we die. The difference is that our lives are measured in centuries instead of years.”

John stiffened for a second, sweat beading on his brow. “Sherlock I am warning you, if I don’t leave soon I’m not going to be able to.”

Sherlock waved his concerns away before resuming his questioning.

“Last March?”

“What?”

“You said you were in Wales at a conference on how to manipulate the incurably dull into liking you-”

“On building trusting relationships with patients,” John corrected dryly.

“But,” Sherlock steamrolled ahead, “I knew you had seen Harry. I figured she was back in rehab and you were just too embarrassed to say anything. Where were you really?”

John shook his head in amazement, more at the surprising display of tact than the deduction. “You really are extraordinary aren’t you? “

A faint blush stole across Sherlock’s cheeks. “You haven’t answered my question,” he chided.

“Fair enough. I _was_ in Wales, but not at a conference. The last two _Dormarch_ offed each other. They'd been fighting like cats and dogs on and off for yonks so I can't say I was surprised.”

Another faint tremor wracked John’s body, and Sherlock knew it wouldn’t be long before a decision had to be made, one way or another.  Once again he was in a position where he knew exactly what he wanted but wasn’t sure how to get it. “So...what did you do? I mean with all your free time,” he clarified hastily. He wasn't sure he was ready to hear about how one went about ‘escorting fallen warriors to the afterlife’ quite yet. “You must have been so bored…”

John looked thoughtful. “I was. To be without purpose is a terrible thing. Most of us can't handle it. So I tried the other side of things. I adopted a human form and I trained as a healer. When that wasn’t enough, I joined the army and fought for king and country instead. It wasn’t what I grew up with but it was enough.” John paused for a moment, a shadow of remembered pain marring his expressive face. “Then Afghanistan happened. When I returned to England, I never thought I would see the battlefield again until I saw Mike that day in the park.  But you showed it to me, here in the blood of London. I was fading away before I met you, Sherlock. You brought me back from the brink.”

Without another word, John turned away to peel off his jumper and vest, placing them carefully over the arm of the chair. Across his back a faded blue tattoo stretched like wings from one shoulder blade to the other. It was a twisted circlet of knots. In the centre a lone hound eternally chased its own tail.

Sherlock leaned forward to get a better look but when John turned to face him, his breath caught in his throat, the tattoo forgotten.

On John’s left shoulder, the ragged crater of a wound split the topography of his skin.

“Oh,” Sherlock murmured, finally understanding why John had never let him catch a glimpse of the wound before. “That is _not_ a bullet wound.”

John shrugged apologetically. “You were half right I suppose, I took a lance to the shoulder during the Second Afghan war. The bastard had it tipped with iron instead of steel. People… uhh...like me are hard to kill but he almost managed it.”

Sherlock rapidly connected the dots. “You knew Mike before the war. I assumed the 2001 war but I doubt lances featured heavily, so that would mean Mike is?”

“A Kelpie actually.”

“Oh,” was all he could think to say, frantically trying to reconcile the plump, spectacled man in his head with a malevolent water horse partial to human sacrifice.

“Don't worry, Mike hasn't drowned anyone since George II was on the throne.”

“Who?”

John smirked at Sherlock’s predictably blank look. “Nevermind, it's been ages. Although if he offers you a piggyback ride by the Thames just say no eh?”

Sherlock looked affronted for a split second before the tension in the air cracked and they both burst out laughing. Something warm swelled inside Sherlock’s chest. Whatever had happened, whatever would happen, they were going to be all right.

***

“So what happens next?” Sherlock asked, a little more cautiously.

“You tell me,” was all John said, watching his friend hungrily, eyes dark and muscles tense.  Sherlock felt his mouth go dry. The formerly unassuming doctor looked ready to eat him alive.

“I already told you. I want it, I want this, you,” he made a vague gesture with his hands, his words for once failing him.

John leant forward and growled low in the shell of his ear. “You don't know what you are asking Sherlock, _if_ we do this, there will be no going back. Everything has a cost...” It was a promise and a warning all in one.

Sherlock nodded, his fingers drifting up to reverently caress the ruined flesh of John’s shoulder.

John swallowed a moan before pushing him away roughly. “Wait.”

“Why?” Sherlock managed to ask in a small voice so unlike his own.

“Because, Sherlock Holmes, if you keep touching me I am going fuck you, and there is no way that you could take me as you are now and live.”

“I don't understand, those women…you didn't?”

John had the good grace to look abashed. “I was careful. No more than once a week, no woman more than twice. But I can't do that with you Sherlock, the way I feel about you. I know I wouldn't be able to control myself. Do you know how hard it is for me to keep this form when I am around you? I would _destroy_ you.”

Sherlock gasped, arousal and fear clouding his mind “But there _is_ a way, that you could...umm...fuck me.” His cheeks burned with a furious blush at his own indelicate language.

“There is always a way, but there would be consequences, for both of us. It wouldn't be just ‘a fuck.’ I would have to share my power, mark you as one of us, as _mine_ , but it would change you...if we share this, we share everything. This would bind us, _permanently_. My life to your life.”

“What do you mean?,” replied Sherlock, struggling to understand.

John paused, trying to put into words that which before he had only known in his blood.

“Picture two hourglasses side by side, each grain of sand represents an hour of our lives. The sand in the top represents the time we have left. What this would do in effect would be smashing the glass and sharing the remaining ‘sand’ between us.”

“Law of conservation of mass and energy,” Sherlock murmured in wonder, his mind abruptly sidetracked by the implication that something as nebulous as ‘magic’ could be bound to natural laws in the same way as mathematics or nuclear physics.

“Something like that. But I am serious, Sherlock. This would change you _physically_ , and can you imagine living a century or two with me?”

“And if I couldn't?” Sherlock replied thoughtfully.

“I leave right now, I come back in a day or two. You keep being brilliant, we solve cases together. You live out your normal human span. I live another four to five hundred years.

“And if we do this, your years would be shared between us. You would give that up for me?” His brow wrinkled in puzzlement.

“Sherlock, if we had met 1,000 years ago I would have gladly shared my remaining centuries with you. As it is I only have a few left but I would gladly share them with you. You wouldn't be bored?”

“Don't be stupid John. Even before this you were endlessly fascinating - I don't think I could plumb your depths if we had a hundred or two hundred more years together.”

“So you do want this?”

“God yes.”

“Alright.” John let out a slow breath through his teeth and leant over to fumble in the end table before pulling out a knife. It was silver and something about the line of the hilt and the curve of the blade spoke of ages past; times both bloodier and simpler. Sherlock could just make out a tracery of celtic knotwork running up the handle like veins, worn almost flat by uncounted years.

Sherlock’s mind stuttered and skipped a beat. He knew John owned nothing like this and at the same time there it was, laying across the palm of his hand like a sliver of moonlight. The other part of him was stuck trying to parse why John had just pulled out a knife. Flashes of facts about ritual sacrifice snapped through his mind like bolts of lightning. _Hearts cut out, throats slashed in homage to dark gods._ But his choice had already been made, he wanted John, no matter what that entailed.

He watched with a stuttering heart as John took the knife and drew it across his own palm, the blood welling up dark as wine.

“Drink,” John commanded.

Sherlock met John’s eyes again and although he couldn’t even begin to understand what was happening,  he trusted the man without measure. With trembling fingers he accepted the proffered palm and brought it to his lips.

John’s blood felt scalding hot across his tongue and didn’t taste the way he expected. It was spicy and seminal with the hint of strange herbs. As he swallowed he felt a warmth spread down his throat, through his chest and right down to the tips of his toes. It made his knees weak and his cock swell.

Sherlock pulled away with a gasp and sunk unsteadily to his knees, his erection pressed painfully against his zip. “John.” It came out as no more than a whimper.

Beside them, the fire in the grate popped and crackled, sending their shadows dancing madly around them. John’s shadow stretched almost luxuriously and for a second resolved into the form of a great hound, the size of a young bull, tail coiled like a whip.

Sherlock gasped but John just chuckled, his smooth muscles jumping in the warm light. “Take your clothes off, I know how you feel about your togs and I would hate to see them get ruined.”

Sherlock swallowed hard, his adam’s apple bobbing in the slim column of his throat. Licking the blood off his lips, he clumsily toed off his shoes and socks and undid his shirt, button by torturous button. He let the garment slide to the floor in a whisper of silk, nipples peaking in arousal under the heat of John’s gaze. He then moved to his belt buckle with trembling fingers. It was a moment’s work to slide the constricting fabric of his trousers and pants over his straining member.

John chuckled warmly in approval before removing his brogues and deftly undoing his own flies. Thrown into sharp relief by the firelight, his muscular frame fairly crackled with power. Sherlock marvelled at how he could ever have thought John was human.  

Rolling through the stillness of the night the great bell of the Palace of Westminster began to toll. It was midnight.

**All Hallow's Eve**

John took a deep breath as spasms chased themselves across his body, muscles swelling and bulging. He shook like a tree in a storm, and Sherlock watched in awe as tendons stretched and bones cracked. The shadow behind him diminished as John grew. The man who stood before him was John and not John; everything he had been but something _more_. Maybe it has always been there and Sherlock had been unable to see. The figure before him was only an inch or two taller than Sherlock but the rugged bulk of his muscles made him look that much bigger. Behind him a sleek tail lashed back and forth in a staccato rhythm of desire. John opened his mouth in a hungry smile, sharp canines shining like knives in the moonlight. He stretched luxuriously, limned by the firelight. Against his hard stomach, his cock jutted up obscenely from a thatch of golden curls. It was un-cut, massively thick and at least eleven inches long. His arousal looked almost painful, skin flushed a dark purple and foreskin completely retracted. A network of pulsing veins running from root to tip throbbed and jumped with every beat of his valiant heart. The vascular lattice reminded Sherlock of the design on the knife’s hilt. Underneath John’s arousal a pair of large pendulous bollocks hung, heavy and full.

As he took in the sight with parted lips, the edges of his friend’s silhouette tickled his vision. Sherlock suddenly knew that even this wasn’t John’s true form. He thought back to the shadow he had seen and realized that at least this was closer.

Against his will Sherlock’s mouth began to water and a helpless moan escaped his mouth.

At the sound of that needy whine, John’s cock visibly twitched and a bead of pre-come wept from the tip and dripped slowly down his member in a glistening trail.

Sherlock, still on his knees, was almost paralyzed with a heady mix of lust and terror. He had of course experimented with his own fingers and even a slim toy but nothing the size of _that_. It looked big enough to split him in two.

“Shhh,” John whispered, “I will take care of you.” His voice gravelly and much deeper than normal.

With those tender words he dragged calloused fingers through the slick still dripping from his slit before smearing it messily over Sherlock’s lips.

For an instant Sherlock tasted the tang of peat fires and animal musk, before a wave of lust crashed over him. It was so powerful that without knowing how, he found himself crouched down on all fours lifting his arse up, begging to be mounted like a bitch in heat.

John chuckled darkly and moved to stand behind him. His pressed his hot length into Sherlock's cleft and began jerking himself mercilessly, chanting quietly under his breath. It was only a few strokes before he gave a mighty growl and ejaculated hotly all over Sherlock's twitching hole.

Sherlock gave a shout of indignation, lust mixed with outrage that he hadn't even been able to touch.

John just laughed, picking him up as though he weighed no more than a kitten, before slamming him roughly up against the wall. He leaned in and plundered Sherlock’s mouth with a kiss, cock still rock hard and pressed insistently against his friend’s leg.

Sherlock moaned at the intrusion before gasping in shock as he felt a blunt finger slick with semen breach him.

“Don't worry _mo chridhe_ \- we are just getting started,” John promised and then renewed his assault on his lips, still working his fingers hard into Sherlock’s waiting hole. Sherlock gasped, caught between pulling away from the intrusion and trying to push himself down for _more._ John growled softly and pulled back to nuzzle into the crook of his neck, alternating soft kisses with nipping bites. Sherlock groaned, his cock trapped damply against his belly. John continued to thrust his finger lightly before pulling out to scoop up more come. Fingers newly slick he introduced a second finger into Sherlock’s passage, the gentle pressure teasing the smooth muscle into relaxing. When John felt the ring begin to ease, he expertly crooked his fingers searching for the sensitive nub. Sherlock arched like a bow string as John began working his prostate masterfully. He alternated between light teasing brushes and firmer massaging strokes. Sparks of light jumped behind Sherlock’s eyes as John introduced a third finger, all the while keeping up an unforgiving torrent of kisses across his collar bones and up the arch of his neck.

Sherlock couldn’t breathe - he couldn’t think, everything was coalescing into a wave of exquisite pressure, starting in his balls and rising up through his groin. He tried to say something, to tell John that he was close. He managed a deep inhale, but dextrous fingers roughly pinched a swollen nipple while the other thrust hard against his prostate and it was too late. He was coming, choking on his breath, ejaculate spraying up across his concave belly, all the way up to his chin. John gave a possessive rumble of satisfaction as Sherlock slumped down bonelessly against the wall.  John was looking down at him like he was something precious - something _extraordinary_. For the first time ever, Sherlock’s mind felt washed as clean as the beach after tide had slid out, all imperfections polished and softened by the implacable power of the sea. All the broken pieces inside him were not mended but they had been smoothed out. The jagged edges of a broken bottle transformed into sea glass and revealed as something beautiful.

John held him there for a minute, the two of them breathing warmly into each other’s mouths before working his way back down his chest to lick him clean with a surprisingly dextrous tongue. To Sherlock’s amazement his own cock began to rise once more, hardening with each beat of his heart until it was standing rigid and hot against his stomach. “John.” The word was a whisper of awe, falling from his mouth like a benediction. John pushed one last burning kiss upon his lips before rising up to his full height and walking towards the window to gaze out over the quiet street. He turned back to look down on Sherlock where he leant panting against the wall.

“It’s time. Last chance to change your mind Sherlock.” John’s voice was rough with desire and hunger. As he stalked slowly towards Sherlock, the air around him flickered, and for an instant the detective was able to see him as he truly was. No more masks. In John’s place was a white hound, the size of a young bull. His shaggy fur and sharp teeth gave him a wolflike cast. Each of his paws were the width of a man’s hand and tipped with silver nails, behind him a long tail waved behind him like a flag.

Sherlock blinked to clear his vision, and deliberately nodded his head in acknowledgement before sinking to his knees in clear invitation. He had come too far to turn back.

John arched an eyebrow playfully before gently pulling him to his feet and guiding him to sit in his arm chair. “Soon, Sherlock, soon…” John licked a wet stripe across his palm before taking his own length in hand and giving it a firm stroke. Pre-come began to dew on the glans before dripping across his fingers. Sherlock moaned brokenly. He didn’t think he could stand to watch John come again without at least having a taste.

John seemed to read his mind and while he continued to stroke his rigid length with torturous slowness, he brought his other hand up to stroke Sherlock’s cupid’s bow. Sherlock groaned at the sensation of the rough digit so close to his mouth and reached out a pink tongue to lap at the skin before sucking the finger in. It tasted of semen and musk and himself. It was the filthiest thing he had ever done. The thought of where that finger had been made a fiery blush rise to his cheeks and his cock twitch, a sharp spike of pleasure knotting his stomach. John groaned in approval before working the finger in and out of his mouth, a pantomime of the more intimate act.

After a few more torturous swipes of his finger he straightened up, taking his rigid shaft in hand before gently guiding it between those plush lips. Sherlock was so hard he was leaking and as John began to thrust slowly in and out he began to fear he was going to come from that alone. With every pump, the briny flavour of pre-ejaculate exploded across his palette and his mouth began to water. He couldn’t make a proper seal around John’s enormous girth so his saliva began to drip in shiny trails across his chin and then down his neck. Sherlock had never been so aroused in his life and as John began to thrust faster and harder it just drove him to higher heights of urgent lust. John thrust deeper and Sherlock felt his throat relax to accommodate the length. A few more hard thrusts and he found himself pressing his nose almost to the base of John's cock. He could smell tea and gun oil, and animal musk. The smell of _John_. It made his cock impossibly harder and he groaned around the firm length in his throat, eyes watering, and fingers digging crescents into the upholstery of his chair. With an almost vicious thrust, John’s cock hardened even further before pulsing and jerking, his seed hot on Sherlock’s tongue. The taste was incomparable and Sherlock’s own cock jerked and spurted as he came untouched and messily all over his own lap. John gave a few more gentle thrusts, cock still pulsing lazily before he gently pulled a dazed Sherlock to the floor.

Sherlock’s cock was still as rigid as ever, wet and messy against his own belly as he lurched to his hands and knees with a pained groan.

“Please John, please - I need it- I need you - I can’t take it any more.” His eyes were filled with tears as the maelstrom of burning desire began to rise inside him, his insides clenching viciously.

John’s smile was wicked as he climbed astride him, his heavy cock resting on Sherlock’s loosened hole. A promise of both agony and ecstasy.  

Sherlock’s need was rising again, heading towards a crescendo. He _wanted_ so badly, he struggled for an instant, trying to reach down to fist his hard cock, but John batted his arm aside, pinning his wrists together. At 6’ and over 12 stone Sherlock knew he wasn't a small man, but compared to John’s muscled bulk he felt almost delicate. His violinist fingers were positively dwarfed by John's rough hands where he held them pinned down. As a calloused palm swept along the delicate arch of his ribs and over his pale throat, he was reminded just how breakable he was in this coupling.  Held pinioned by the beast at his back, he was completely at John’s mercy. He knew that even if he struggled he would be unable to break free. His pleasure was completely in John’s hands. The thought of being complicit in his own helplessness caused him to sag in relief and shot a silvery bolt of arousal from his balls to the tip of his weeping cock.

John looked down on where Sherlock’s slim form was captive beneath him, his damp curls a riot of ebony tangles. For a moment he froze, awestruck that the mad genius would submit to him so freely, that he would give up his humanity without a second thought. It was so heady he couldn’t contain himself any longer. Chanting once more under his breath, John began to rub the dripping head of his cock over the slick entrance, Sherlock gasped in desperation at the agonizingly slow glide. John could feel the golden filaments of his magic begin to smoulder, gathering around his lover like static electricity. John gritted his teeth, there was nothing he wanted more than to slam into that tight heat with brutal force but he had to wait. He could already sense the changes happening in his lover, but there was no forcing it. Instead he had to ride the knife’s edge of desperate lust, his tail beating a staccato tattoo of denial.

With the scent of burning iron suddenly wafting through the air, the tendrils of magic ignited. The change had begun. Sherlock screamed in pain mixed with pleasure, his fingers scrabbling uselessly for purchase across the hardwood. That was the sign John was waiting for. With a growl, he grabbed his rigid cock by the base and sank in right to the hilt.

Sherlock keened. The burning stretch and unyielding pressure on his prostate was extraordinary. It was unbearable and he wanted more.

What seemed like eons passed before John began to thrust, slowly at first, then building up to a punishing rhythm, his heavy balls slapping against the creamy flesh of Sherlock’s legs with every pump.  

It was a rough, possessive mating, as John pounded him harder and harder, Sherlock didn't know how much more he could take. He was so painfully full, nerves singing and the tension inside him spooling higher and higher. Sherlock couldn't help crying out, screaming his pleasure and agony to the stars far above Baker Street, the love for John burning him inside and out. The feel of the strong arm pinning him down, fucking his slim body over and over again was almost too much to take. But for John he would do anything. He was so full he felt like he was being split in two, the sensation so all-consuming in its intensity he didn’t know if he could survive. He had a choking moment of panic, John’s words from before echoing through his head. _There is no way that you could take me as you are now and live_. But even as he felt the brink closing dark upon him, he felt a wave of something rising in counterpoint. A flash behind his eyes, burning sodium oxalate and devotion, and the brink receded. Sherlock howled, the magic flowing through his veins transmuting any residual pain into blinding pleasure.

***

As the fire died down to embers John knew it was time. He could feel his knot beginning to form. With every thrust, the pressure on his cock increased as the engorged flesh swelled. He gripped Sherlock’s slim hips with bruising force as he forced the knot against the softened ring of muscle, over and over again. He could feel the power rising to a crescendo inside him along with his orgasm. Underneath him, Sherlock was a trembling wreck, keening and sweating like a lathered horse. John gave one last mighty thrust, and as he came in a hot flood of seed, bit down hard on the back of Sherlock’s neck. As the blood flooded into his mouth the magic spilled through him and into his beloved. Sherlock went rigid in a silent scream, cock spurting and jerking, then slumped bonelessly in a dead faint. John released his jaws and lowered him gently to the ground, laving the bite as aftershocks of his orgasm burned through him like wildfire. There was a blinding flash of light and when the afterimage faded, John watched in awe as across Sherlock’s shoulder blades, a fine tracery of knot work, the blue of the mist over the fen appeared on his skin in an exquisite tattoo. It was done.

**One month later**

The buzzing of the phone shattered the somnolent calm of the bedroom as it vibrated urgently across the night table with a text alert. From underneath a nest of blankets, a pale arm shot out to grab it.

Sherlock swiped a dextrous finger across the screen, squinting in the blueish light.

“Wake up John - we have a case.”

From underneath the duvet came a sleepy growl.

“Looks like it could be a _Bauchan_ ,” Sherlock prodded the warm lump of covers with a bare foot.

John shot bolt upright, the traces of sleep chased away by the jolt of adrenaline. “Really?”

“Nope.” Sherlock popped the ‘p’ with a cheeky wink. “Although we do have a bride who disappeared from her own wedding reception.”

John gave a warm huff of a laugh before sliding out of bed to rummage around on the floor for a shirt and trousers.

A few moments later the doctor and his detective headed off into the night, the shadow of two great hounds following eagerly at their heels.

 

Endnotes: 

_Samhain - October 31,  seen by the ancient celts as_ [ _liminal_ ](https://en.wikipedia.org/wiki/Liminality) _time, when the boundary between this world and the_ [ _Otherworld_ ](https://en.wikipedia.org/wiki/Celtic_Otherworld) _could more easily be crossed_

_Sgùrr a' Ghreadaidh - “The peak of Torment,” the highest summit on the northern half of the Black Cuillin mountain range on the Isle of Skye (Northern Scotland)_

_Tir na Marbh - The land of the dead_

_Dormarch - a mythological hound found in Wales said to have one head and three fish tails._

_Mo chridhe - a Scots Gaelic endearment translating roughly to ‘my heart’_

_Bauchan - A type of hobgoblin from Scottish folklore_

_You can see the reference image for the art[here](http://t.umblr.com/redirect?z=https%3A%2F%2Fwww.google.ca%2Fsearch%3Ftbm%3Disch%26tbs%3Dsimg%3ACAQSlwEJgt5Onz0zTnYaiwELEKjU2AQaBAgCCBgMCxCwjKcIGmIKYAgDEijQG98QvBDHG80bzxvdH-EQzBvcH6w7wi_1nOsMv7i7NLsI86i7mOqs7GjAAJW-pm-1NzO75nzLaFEacze7dLkVhyOenJlrmwMXHffmyq9oA2jxRFCdcaTl9PZkgAwwLEI6u_1ggaCgoICAESBN_1X5x8M%26sa%3DX%26ved%3D0ahUKEwiHqrG75dPNAhWH24MKHZ_tCfkQwg4IGygA%26biw%3D1366%26bih%3D601%23imgrc%3Dv2JnsYfIMLJuqM%253A&t=MWI4MjE3Yzc5M2Y0ZWFhM2YwYmNiOTZmOWJmMjc3NWE3NzM3NDE2MixCWWd6aDV1SA%3D%3D) and in the Book of Kells.  
_

Extra points and a free ficlet of your choice to anyone who figures out who I imagined John’s father was… Update - We have a winner! John's father is Cú Chulainn (Culann's Hound). Congratulations Laguzrising!

 

 

 

 


End file.
